Challenge Library
Coding Challenges
5,893 curated questions across every arena — browse by topic, then jump into a live 3-minute battle to put them to the test.
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1,828 challenges matching your filters
- Multiple ChoiceBeginner
Rule of three
rule-of-threerefactoringdry - Multiple ChoiceBeginner
Composition over inheritance pitfalls
compositioninheritancecoupling - Multiple ChoiceBeginner
ISP and fat interfaces
ispsolidinterfaces - Multiple ChoiceBeginner
Hexagonal adapters for third-party SDKs
hexagonaladapterthird-party - Multiple ChoiceBeginner
Adapter vs facade
adapterfacadepatterns - Multiple ChoiceBeginner
Strategy vs state vs policy
strategystatepatterns - Multiple ChoiceBeginner
Template method vs strategy
template-methodstrategypatterns - Multiple ChoiceBeginner
What an ADR Records
adrdocumentationdecision-records - Multiple ChoiceBeginner
Cost of Change Meaning
cost-of-changeeconomicsarchitecture - Multiple ChoiceBeginner
Technical Debt Definition
technical-debtarchitecturetradeoffs - Multiple ChoiceBeginner
The Technical Debt Quadrant
debt-quadranttechnical-debtfowler - Multiple ChoiceBeginner
Deliberate vs Accidental Debt
technical-debtdeliberate-debtdebt-quadrant - Multiple ChoiceBeginner
Reversibility of Decisions
reversibilitydecisionstradeoffs - Multiple ChoiceBeginner
Just-In-Time Architecture
just-in-timelean-architecturedecisions - Multiple ChoiceBeginner
YAGNI at Architecture Level
yagnisimplicityarchitecture - Multiple ChoiceBeginner
C4 Model Diagram Levels
c4-modeldiagramsdocumentation - Multiple ChoiceBeginner
Canary vs Blue-Green Deployment
progressive-deliverycanaryblue-green - Multiple ChoiceBeginner
Parallel Change for APIs
parallel-changeexpand-contractapi-evolution - Multiple ChoiceBeginner
Stateless services and sticky sessions
system-designscalability - Multiple ChoiceBeginner
Vertical vs horizontal scaling limit
system-designscalability - Multiple ChoiceBeginner
L4 vs L7 load balancer
system-designload-balancing - Multiple ChoiceBeginner
Consistent hashing vs modulo hashing
system-designload-balancingconsistent-hashing - Multiple ChoiceBeginner
Cache-aside vs write-through
system-designcaching - Multiple ChoiceBeginner
Write-back cache risk
system-designcaching - Multiple ChoiceBeginner
LRU vs LFU eviction
system-designcachingeviction - Multiple ChoiceBeginner
Negative caching
system-designcaching - Multiple ChoiceBeginner
CDN purpose
system-designcachingcdn - Multiple ChoiceBeginner
Cache penetration
system-designcaching - Multiple ChoiceBeginner
Read replica lag
system-designdatabasesreplication - Multiple ChoiceBeginner
SQL vs NoSQL access pattern
system-designdatabasesnosql - Multiple ChoiceBeginner
Index write amplification
system-designdatabasesindexes - Multiple ChoiceBeginner
Leader election with consensus
system-designconsensusleader-election - Multiple ChoiceBeginner
CAP theorem statement
system-designcap-theorem - Multiple ChoiceBeginner
Causal consistency
system-designconsistency - Multiple ChoiceBeginner
Eventual consistency tradeoff
system-designconsistency - Multiple ChoiceBeginner
At-least-once semantics
system-designmessagingidempotency - Multiple ChoiceBeginner
Dead letter queue
system-designmessagingdlq - Multiple ChoiceBeginner
Poison message and head-of-line blocking
system-designmessagingdlq - Multiple ChoiceBeginner
Token bucket burst behavior
system-designrate-limiting - Multiple ChoiceBeginner
Sliding window log memory cost
system-designrate-limiting - Multiple ChoiceBeginner
Cursor vs offset pagination
system-designapi-designpagination - Multiple ChoiceBeginner
API versioning rationale
system-designapi-designversioning - Multiple ChoiceBeginner
SLI vs SLO vs SLA
system-designobservabilityslo - Multiple ChoiceBeginner
p99 vs mean latency
system-designobservabilitylatency - Multiple ChoiceBeginner
Blob vs object storage
system-designstorages3 - Multiple ChoiceBeginner
Inverted index
system-designsearchinverted-index - Multiple ChoiceBeginner
URL shortener key generation
system-designurl-shortenerunique-id - Multiple ChoiceBeginner
Snowflake ID structure
system-designunique-idsnowflake - Multiple ChoiceBeginner
Service discovery
system-designservice-discovery - Multiple ChoiceBeginner
Liveness vs readiness probe
system-designhealth-checkskubernetes - Multiple ChoiceBeginner
Storage sizing with replication
system-designcapacity-estimationstorage - Multiple ChoiceBeginner
Bandwidth estimation
system-designcapacity-estimationbandwidth - Multiple ChoiceBeginner
SQS visibility timeout
system-designmessagingsqs - Multiple ChoiceBeginner
Cache warming
system-designcaching - Multiple ChoiceBeginner
Idempotent HTTP methods
system-designapi-designidempotency - Multiple ChoiceBeginner
Distributed tracing purpose
system-designobservabilitytracing - Multiple ChoiceBeginner
Failover active-passive vs active-active
system-designavailabilityfailover - Multiple ChoiceBeginner
Nines and downtime budget
system-designavailabilitynines - Multiple ChoiceBeginner
Back-of-envelope QPS from DAU
capacity-estimationqpsback-of-envelope - Multiple ChoiceBeginner
Why negative caching helps
cachingcache-penetrationnegative-caching
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